Unusual larviform beetles in 100-million-year-old Kachin amber resemble immatures of trilobite beetles and fireflies

Abstract

Despite the large number of species in the group Coleoptera (beetles), it is usually relatively easy to identify an adult beetle as such due to certain common characteristics. Among beetle larvae, however, there is a larger variability of body organisation. In some lineages, specialised larval morphologies are carried on into the adult phase by heterochrony, more exactly paedomorphosis. Such evolutionary events resulted in larviform females, as they occur in some extant representatives of Lycidae (net-winged beetles) and Lampyridae (fireflies). However, such larviform individuals, larvae or paedomorphic females, have been very rarely described in the fossil record until now and were restricted to Cenozoic ambers. Here, we report fossil larviform representatives, resembling larvae of the groups Lampyridae and Lycidae in certain aspects, from 100-million-year-old Myanmar amber. We furthermore discuss the morphological similarities and differences of the three new specimens in relation to extant larviform representatives of the groups and possible relationships of the new fossils.